1. Technical Field
The present invention relates to a waterproof switch device provided with a structure capable of preventing any intrusion of water.
2. Related Art
An automobile is provided with a power window switch for controlling the opening/closing of a window. In general, a power window switch includes: an oscillatable operating knob that is manually operated; a circuit board having a contact unit for outputting a signal in response to the operation of the operating knob; a case containing the circuit board therein; and a cover that is fitted to an opening formed at the lower portion of the case so as to cover the opening.
In the above power window switch, a raindrop intruding through an open window or a spilt beverage (hereinafter generically referred to as “water”) may intrude into the case. And then, the water intruding into the case adheres to the circuit board, thereby inducing short-circuiting of an electric circuit or corrosion of the contact unit so as to cause an erroneous operation of the switch. Japanese Unexamined Patent Publication Nos. 9-265851, 2006-120468, and 9-204842 disclose a structure for preventing such intrusion of water.
Japanese Unexamined Patent Publication No. 9-265851 discloses a power window switch provided with a structure for allowing a projection formed at the side surface of a lower case (i.e., a cover) to be fitted to a hole formed at the side surface of an upper case, the switch including a rib surrounding the hole formed at the side surface of the upper case, wherein the rib guides downward water flowing down from the upper surface of the upper case along the side surface thereof and drains it. However, this structure has a fear of the water intrusion into the hole because of a capillary phenomenon since the water flows over the rib to the vicinity of the hole in the case of the large amount of water flowing down from the upper surface of the upper case.
As a countermeasure against this, Japanese Unexamined Patent Publication No. 2006-120468 discloses that a groove spaced from a side surface of an upper case is formed around a projection formed at the side surface of a lower case (i.e., a cover), so that a predetermined interval is secured between the periphery of the projection formed at the lower case and the hole formed at the upper case. In this manner, even if water flows in the vicinity of the hole formed at the upper case, the interval can inhibit any intrusion of water into a container because of a capillary phenomenon.
Japanese Unexamined Patent Publication No. 9-204842 discloses a power window switch including eaves covering the upper portion of a connector provided at the side of a case, an upper water stopping wall erected at the front edge of the eaves, and a side water stopping wall covering both sides of the connector. In this switch, the eaves receive the water flowing from the upper portion of the case, and then, the upper water stopping wall guides the water toward the side water stopping wall so as to make the water flow along the side water stopping wall, thus preventing the intrusion of the water toward the connector.
As described above, there have been conventionally proposed the various kinds of techniques for preventing any intrusion of water flowing downward from a side surface of a case into the inside thereof. However, the water intruding into the case intrudes into the case not only from the side surface of the case but also from the back of the case. Although the back of the case is closed with a cover, the water intrudes into the inside through a minute clearance defined between the case and the cover because of a capillary phenomenon.